He was the pilot of the third flight of the space shuttle Columbia in March 1982, and commanded the Challenger flight that carried the second Spacelab mission in June 1985. Fullerton became a crew member of the Manned Orbital Laboratory programme in 1966 until its termination in 1969. He was subsequently transferred to NASA as an astronaut. After logging 380 days in space, he ended his astronaut service in 1986 and in 1988 became a research pilot at NASA's Dryden Flight Research Center. He retired as Associate Director of Flight Operations at Dryden in 2007.